The development and validation of an instrument designated as the Classroom and School Community Inventory (CSCI) are described. Scores on both the classroom form and the school form of the CSCI possess strong content validity, construct validity, internal consistencies, and 2-week test-retest reliability. Using a sample of 341 traditional and online students, confirmatory maximum likelihood factor analysis with oblique rotation provides empirical support for the conceptual distinctions between the latent dimensions of social community and learning community in both forms and for the existence of classroom and school communities as separate but related constructs. The two factors of the classroom form account for 70.73% of the variance in the data, and the two factors of the school form account for 63.54% of the variance. (Contains 8 tables.)